This application for a Translational Research Center in Thrombotic and Hemostatic Disorders describes research to develop a novel class of antithrombotic agents. Component projects explore protein disulfide isomerase (PDl) as an antithrombotic target using isoquercetin, quercetin 3-rutinoside and quercetin as inhibitors of PDl. In Project #1, Dr. Bruce Furie, with Dr. Barbara Furie and Dr. Mingdong Huang, explore the mechanism by which PDl participates in thrombus generation and will test in vivo thrombosis models whether PDl inhibitor can prevent thrombosis in mice. Dr. Huang will solve the crystal structure of PDl with and without a bound PDl inhibitor. In Project #2, Dr. Robert Flaumenhaft and Dr. Natalia Beglova will search for more potent PDl inhibitors at the Broad Institute. PDl domains will be expressed and their interaction with small molecule PDl inhibitors examined by NMR spectroscopy. New ligands will be designed, synthesized by chemists at the Broad Institute and subsequently tested. This project will expand the number of PDl ligands available for evaluation in this new class of antithrombotics. In Project #3, Dr. Jeffrey Zwicker, with Dr. Donna Neuberg, will explore the antithrombotic properties of quercetin and isoquercetin in humans, agents approved for human use. A pharmacokinetic study with quercetin and isoquercetin in the presence and absence of ascorbic acid will be performed to determine optimal delivery. The effectiveness of the PDl inhibitor in three separate human studies will be evaluated: thromboembolic events in patients with cancer; heparin-induced thrombocytopenia and thrombosis; anti-phospholipid syndrome. This TRC-THD will include four cores that will provide support to the overall program. The Administrative Core (Core A) will be directed by Dr. Bruce Furie, and will coordinate the activities of the three projects. The Intravital Microscopy and Animal Core (Core B) will be directed by Dr. Barbara C. Furie. The Molecular and Structural Biology core (Core C) will be co-directed by Dr. Mingdong Huang and Dr. Natalia Beglova. The Translational Skills Development Core (Core D) will be directed by Dr. Kenneth Bauer. The Center will work to develop a new class of antithrombotic agents directed against PDl with both antiplatelet and anticoagulant properties.